1. Field of the Invention
The present invention relates to an organic transistor and a manufacturing method of an organic transistor having an organic semiconductor layer and a semiconductor device having an organic transistor.
2. Description of the Related Art
A field-effect transistor controls an electric conductivity of a semiconductor layer which is provided between source and drain electrodes with a voltage applied to a gate electrode, and a field-effect transistor is a representative one of unipolar elements using carrier transport of either holes or electrons.
Since various kinds of switching elements and amplifying elements can be formed depending on a combination of such field-effect transistors, these field-effect transistors are applied in various fields. For example, a switching element of a pixel in an active matrix display or the like can be given as the application.
An inorganic semiconductor material represented by silicon has been used broadly as a semiconductor material using for the field-effect transistor. Since a high-temperature treatment is needed for forming a film of an inorganic semiconductor material as a semiconductor layer, it is difficult to use plastic or a film as a substrate.
In contrast with this, since a film can be formed at even low temperature relatively, a field-effect transistor can be manufactured in principle over a substrate of which heat endurance is low such as a plastic substrate as well as a glass substrate when an organic semiconductor material is used as a semiconductor layer.
An organic transistor which is formed by forming a film the semiconductor layer including the organic semiconductor material in a low temperature process is disclosed in Patent Document 1. Note that a gate insulating film of the organic transistor written in Patent Document 1 is formed by a plasma CVD method.
[Patent Document 1]
    Japanese Patent Laid-Open No. 2000-174277
With a minituarization of the transistor, it is necessary to make the gate insulating film thinner at the same time as shortening a channel length. However, when the gate insulating film is made thinner, a tunnel leakage current is high, and there is a concern about degradation of reliability. Therefore, the gate insulating film which is a higher resistant property is needed.